Organic compound



yields obtained.

Patented Feb. 15, 1944 UNITED STATES PATENT OFFICE.

ORGANIC COMPOUND Roger Adams, Urbana, 111., assignor to E I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware -No Drawing. Original application July 27, 1940, Serial No. 348,072, now Patent No. 2,325,727, dated August 3, 1943. Divided and this application February 20, 1942, Serial No. 431,716

4 Claims. (Cl. 260-586) This invention relates to the preparation of new and valuable organic compounds and more particularly -to the preparation of new diaroylcyclohexenes which are valuable intermediates in the preparation of 1,3-diaryl-4,7-dihydroisobenzofurans. This application is a division of copending application Serial No. 348,072, filed July 27,

In U.- S. P. 1,944,731 a specific application of the Diels-Alder reaction is disclosed wherein such compounds as butadiene or other unsaturated compounds containing conjugated double-bonds are condensed with unsaturated ketones, acids,

aldehydes, etc. to produce organic compounds having hydrogenated ring systems. 7

It is the object of this invention to prepare new organic compounds which can be readily converted to 1,3-diarylisobenzofurans which have beenfound to be valuable, particularly as fluorescent colors for hydrocarbon oils. It is a further object of the invention to prepare new organic compounds of the 1,3-diaryl-4,7-dihydroisobenzofuran series and the diaroylcyclohexenes which are employed in their preparation.

1,3-diphenylisobenzofuran of the formula has been prepared in several ways which are, however, not of commercial interest because of the Ithas been found that the higher molecular weight 1,3-diarylisobenzofurans are of value as fluorescent colors for use in lubricating oils,- but the methods heretofore disclosed for the preparation of the simple compounds of this class are not suitable for commercial production of these new higher molecular weight compounds.

I have found that the 1,3-diaryl-4,7-dihydroisobenzofurans-of the formula;

H: aryl I o/ V H1 aryl which can be readily and economically converted to the 1,3-diaryl-isobenzofurans, may be pro- .duced by the addition of butadiene or its substitution derivatives and 1,2-diaroy1ethylenes to g1vediaroylcyclohexenes. which in turn are consulfuric acid to effect a simultaneous dehydration and ring-closure to the furan ring. Where substituted 1,3-diary1-4,7-dihydroisobenzofurans 'are to be produced in which the substituents are in the partially hydrogenated benz-ring, substituted butadienes are employed. By using 1,4- disubstituted-butadienes in this synthesis, 4,7-disubstituted-dihydroisobenzofurans are obtained. In a similar manner by the use of 2,3-disubstituted-butadienes, 5,6-disubstituted 4,7-dihydroisobenz ofurans are obtained. By employing various diaroylethylenes a large number of 1,3-diaryl-4,'7-dihydro-isobenzofurans may be obtained.

The general process for preparing these new compounds may be illustrated as follows:

CH OH-C O-GaHs I II EIJH OH-O OCaHs 0H2 Buta- Dibenzoyldiene ethylene CaHs CH2 H 5 4 =C (IT/H CH-COCuH5 A020 3 2O 1 on CH-"COC6H5 H 6 7 c CH7 H2 H! Dibenzoyl-cyclohexene 1,3-diphenyl-4J dihydro-isobenzofuran The various diaroylethylenes and substituted butadienes which may be used in this synthesis will be readily apparent and may be obtained byany of several known methods. The diaroylethylenes may be prepared, for instance, by the Friedel- Crafts reaction of fumaryl chloride upon aromatic hydrocarbons.

As examples of the butadienes which may be employed may be mentioned butadiene, 1,4-dimethylbutadiene, 2,3-dimethy1butadiene, and

their higher homologues, the 1,4- and 2,3-diphenyl butadiene and their homologues.

The 1.2-diaroylethylenes which may be employed may be illustrated by dibenzoylethylene, ditolylethylene, dinaphthoylethylene, di-p-chlorobenzoylethylene, 1,2-trans-di- (p-xenoyl) -ethylene, etc. The invention also contemplates the use of the higher diaroylethylenes such as those which may be produced, for instance, by the" Example 1 A solution of parts of butadiene in 1'75 parts of benzene is prepared by cooling the benzene and passing in butadiene gas until the desired amount is dissolved. Six parts of 1,2-trans-di- -(p-xenoyl) -ethylene are then added and the mass is heated at 100 C. for 3 hours under pressure with constant agitation. Concentration of the resulting benzene solution gives the l,5-di-(p- "xenoyl) -cyclohexene-1,2- as a white crystalline product with a melting point of 267-268 C.

"(Cor.)

Example 2 .A suspension of 6 parts of the 4.5-di-(pxenoyl)-cyclohexene-1,2 in 2'70 parts of acetic anhydride is heated to reflux. As soon as the solvent begins to boil vigorously, asmall amount of concentrated sulfuric acid is added. The suspended compound is immediatelydissolved and the solution exhibits a characteristicfluorescence. Refluxing is continued for a short time and the solution is then cooled,.whereupon the 1,3-di-(pxenoyl) -4,7-dihy.dro-isobenzofuran separates out in fine yellow crystals. The product is removed by filtration and washed with methanol or recrystallized frombenzene. Itis obtained'as fine yellow crystals having a melting point of 238-239 C. (Cor.). In organic solvents the 1,3-di-(pxenoyl)-4,7-dihydroisobenzofuran dissolves with a yellow-green fluorescence.

Example 3 yellow crystalline product having a melting point of 239-240" C. (Cor.).

Example 4 A mixture of parts of 1,2-dibenzoylethylene, 41 "parts of IA-dimethylbutadieneand parts 'of-tolueneare heated under reflux for 18 hours.

The solvent is then evaporated to concentrate the residue to a syrupy mass and while still hot 120 parts of methanol'are added. On cooling ,the solution sets to a crystalline mass. It is then .refiuxed for 20 minutes.

methanol mother liquor an isomeric adduct having a melting point of 86- 88 C. may be obtained.

A solution of 10 parts of the 3,6-dimethyl-4,5- dibenzoylcyclohexene-LZ in a mixture of parts of glacial acetic acid and 43 parts of acetic anhydride and 0.5 part of 85% phosphoric acid are The solution is poured into water, extracted with chloroform and the solvent is removed under vacuum. The resulting mass is crystallized on slurrying with warm methanol. The l,3-diphenyl-4,'l-dimethyl 4,7-

.dihydroisobenzofuran on recrystallization from methanol is obtained in crystalline form with a melting point of 114-115 C.

Example 5 r (unredistilled dehydration product of pinacol with 48% hydrobromic acid). The mixture is refluxed for 3.hours and allowed to cool, whereupon the 1,2-dimethyl-4,5-dibenzoylcyclohexene crystallizes out. On recrystallization from.9,5% ethanol it is obtained in crystal form having a melting-point of 111-1 11.5? C. (Cor.)

By subjecting the 132-dimethyl-4,5-dibenzoylcyclohexene to the dehydration ring-closure reaction as described in the previous example 1,3- diphenyl-5,6-dimethyl-4,7 dihydroisobenzofuran is obtained as yellowish-green fluorescentcrystals having a melting point of 225+226 C. (Cor.). This product when dissolved in organic solvents. exhibits a blue fluorescence. Insulfuric acid it gives an orange brown color.

Example T6 To a cooled solution of 15 parts of butadiene in 175 partscf'benzene are added 40 parts of trans-dibenzoylethylene. Themixture is heated 'under pressure for 2 hours at C. The benzene is then evaporated to about one-half its volume and 100 partspf methanol are added. Upon cooling the 4,5-dibenzoyl-cyclohexene separates out. On recrystallization from ethanol it is obtained as white crystals having a melting point of 111.5112 C. When the 4.5-dibenzoylcyclohexene is-subjected to the dehydration ringclosure reaction as described in Example 4, the 1,3 diphenyl 4,7 dihydroisobenzofuran is obtained, whichon recrystallization from petroleum ether isin the form of yellowish-green crystals having a melting pointof -121 C. (Cor.).

In a similar manner to that described in the above examples 1,2-di-p-chlorobenzoylethylene tained having a melting point of 151 C. which may be converted to the 1,3-di-p-chlorophenyl- 5,6-dimethyl-4,7-dihydroisobenzofuran, having a melting point of 236 C.

Di-p-toluylethylene condensed with 2,3-dimethylbutadiene gives 1,2-dimethyl-4,5-di-ptoluylcyclohexene having a melting point of 129 C. which in turn may be converted to 1,3-di-pt0ly1-5,6-dimethy1-4,7-dihydroisobenzofuran having a melting point of 237 C.

Where 2,3-diphenylbutadiene is condensed with dibenzoylethylene the l,2-diphenyl-4,5-dibenzoylcyclohexene is obtained, which when subjected to the dehydration ring-closure reaction is converted to 1,3,5,6-tetraphenyl-4,7.-dihydroisobenzofuran which on recrystallization from toluene has a melting point of 272-274 C. The 2,3- diphenylbutadiene may be obtained by the meth- 0d described by Allen et a]. in the Journal of Canadian Research, February 1938.

By the substitution of other diaroylethylenes, particularly those containing aroyl groups of high molecular weight, a large variety of 1,3- diaryldihydroisobenzofurans may be obtained which are valuable as intermediates in the preparation of oil fluorescent colors.

Iclaim:

1. Diaryl substituted 4,5-dibenzoylcyclohexems-1,2 which carry the two aryl groups in one of the pairs of positions 1,2 and p'-p"-positions on the benzoyl groups.

2. 4,5-di(p-xenoyl) -cyclohexene-1,2.

3. 1,2 dimethyl-4,5-di-(p-xenoyl) cyclohex- (me-1,2.

4. 1,2-diphenyl-4,5-dibenzoyl-cyclohexene.

v ROGER ADAMS. 

